std.fs: Fix Walker closing the initial directory when not fully iterated
This is a fix for a regression caused by https://github.com/ziglang/zig/commit/61c5d8f8f19d4321a492cb8a1adc4d221024f7d9
Closes #12209
4624c81899Ryan Liptak committed on 7/24/2022, 7:00:14 PM· committed by Andrew Kelleyparent934573f